Vacuum conveyor belts for holding articles by vacuum pressure and for moving articles between first and second positions are known in the art and include a variety of features for conveying different types of articles.
U.S. Pat. Nos. 3,080.079 (Lecrone) and 4,773,522 (Lenhart) disclose overhead vacuum belts for lifting articles off a conveyor. Lecrone includes means for aligning baking trays on the conveyor, and a transfer belt for receiving buns removed from the trays by the overhead vacuum belt. Lenhart includes a vacuum deadplate for accumulating and metering articles to the overhead vacuum belt in rows.
U.S. Pat. Nos. 4,530,632 (Sela) and 3,722,665 (Probasco) disclose vacuum conveyor belts for transferring a single file of articles up an incline. Sela includes a vacuum belt formed of open mesh and a air conveyor delivery chute. Probasco includes a spring-biased vent in the vacuum chamber to regulate vacuum force in accordance with the number of articles on the belt to assure initial pickup but prevent excessive force.
Infeed boots, such as that illustrated in FIG. 4, for loading vacuum conveyors are also known in the art. Prior art infeed boots include an article-retaining surface adjacent the vacuum elevator belt. This surface helps to prevent articles, which generally enter the boot on their sides, from tipping over. Tipped articles may be damaged and may also jam the boot.
A disadvantage of prior art infeed boots is that articles entering the boot wall-up along the entry guide effectively forming a secondary vacuum chamber in combination with the article retaining surface. The secondary vacuum chamber draws air in through its open side, i.e., its exit, in a direction opposite the vacuum conveyor belt conveying direction. This flow of air in through the boot exit may impede the passage of articles out through the boot exit and may require higher pressures to retain articles on the vacuum belt. Higher pressures, however, are likely to increase the air flow into the boot exit. Further, higher pressures may concentrate incoming articles on the edge of the vacuum belt nearest the boot entrance.
What is desired, therefore, is an infeed boot which reduces the flow of air in through the boot exit, and which permits adjustment of the distribution of articles across the vacuum conveyor.